Police detectives are investigating the circumstances around the death of a four-month-old baby in Bunbury, south of Perth.
A man and a woman are assisting police with the investigation.
The baby girl was taken to Bunbury Regional Hospital last Friday before being transferred to Perth by the Flying Doctor Service.
She died on Sunday in Princess Margaret Hospital.
Police have interviewed an 18-year-old woman and 21-year-old man, but have not laid charges.
The Major Crime Squad is investigating and a post-mortem examination will be done to determine the cause of the baby’s death.